1. Field of the Invention
The present invention relates to a data processing apparatus and a print data generating method, and more particularly, to technology that generates binary print data using dot arrangement patterns for the quantization of image data.
2. Description of the Related Art
This kind of dot arrangement pattern is a pattern that determines, for image data containing individual pixels at a horizontal and vertical resolution of 600 dpi for example, whether each of pixels in 1-pixel by 2-pixel ranges at 1200 dpi with double resolution in the vertical direction is a “printing (dot)” pixel or a “non-printing (no dot)” pixel, according to the gradation value of the image data. Then, with binary data generation, a dot arrangement pattern corresponding to the gradation values indicated by the image data may be used to convert the gradation values indicated by the 600 dpi image data into binary data (dot/no dot) in the 1-pixel by 2-pixel ranges. According to such binarization technology, data can be processed and transmitted at low resolution, thus preventing long data processing and transmission times, while in addition, the memory capacity in the printing apparatus can be reduced.
Japanese Patent Laid-Open No. 2004-90462 describes binary data generation technology using dot arrangement patterns as described above. Specifically, provided that the above 1-pixel by 2-pixel patterns are treated as single units, a 4-unit by 4-unit matrix is repeatedly applied to image data at a resolution of 600 dpi in the vertical and horizontal directions to generate binary data.
However, simply applying the technology disclosed in the above Japanese Patent Laid-Open No. 2004-90462 produces periodic patterns (textures) in the printed image, which correspond to the size of the 4-unit by 4-unit matrix that acts as the base unit. These textures may lower image quality. More specifically, by repeatedly applying patterns in which the 1-pixel by 2-pixel units constituting the 4-unit by 4-unit matrix having fixed relative positions, patterns of concentration and dispersion are produced in the layout of the 1-pixel by 2-pixel units over the entire printed image, and these patterns appear as periodic textures.